vim: Fix incorrect bracket matching for symmetric quotes in cs operator

[lingyaochu]

Context

Closes #46698

This PR fixes a bug where the cs (change surrounds) operator fails on symmetric delimiters like quotes.

In a sequence like c s ' ", Zed previously performed two independent searches. For a line like I'm 'goˇod', the first step (cs') correctly moves the cursor to the second quote: I'm ˇ'good'. However, when the replacement character " is pressed, change_surrounds would perform another scan from the new cursor position. Because quotes are symmetric, this second search would incorrectly match 'm ' as the target pair, leading to a broken result like I"m "good'.

I've refactored the workflow to ensure the search happens only once. prepare_and_move_to_valid_bracket_pair now computes and stores the Anchor positions of the detected pair directly into the operator state. change_surrounds then simply reuses these anchors instead of re-executing the search. This ensures correctness for quotes while remaining consistent with Vim/Neovim cursor behavior. While this slightly increases coupling between these two functions, it is an intentional trade-off since they exclusively serve the cs operation.

How to Review

The main changes are in crates/vim/src/surrounds.rs. I renamed check_and_move_to_valid_bracket_pair to prepare_and_move_to_valid_bracket_pair and updated it to return the detected bracket anchors. In change_surrounds, I removed the redundant search logic and updated it to perform the replacement using the provided anchors. You can also see the updated Operator::ChangeSurrounds enum variant in crates/vim/src/state.rs which now carries the anchor data.

Self-Review Checklist

• I've reviewed my own diff for quality, security, and reliability
• Unsafe blocks (if any) have justifying comments
• The content is consistent with the UI/UX checklist
• Tests cover the new/changed behavior
• Performance impact has been considered and is acceptable

Release Notes:

• Fixed an issue where the cs Vim operator incorrectly identified symmetric quotes in certain contexts.

[ConradIrwin]

Thanks for fixing this!